While the invention is subject to a wide range of applications, it is especially suited for automotive steering applications and will be particularly described in that connection.
Among the problems involved in universal joint drive connections is the transmission of fluctuating angular velocity. In other words, a given rotation of the driving shaft does not necessarily result in an equal rotation of the driven shaft. Further, an increase in the angle between the driving shaft and the driven shaft causes an increase in the fluctuation of angular velocity.
Another problem found in universal joints is that clearances are required to allow the joint to rotate without binding. However, this clearance causes a backlash in the joint which is undesirable.
U.S. Pat. No. 3,406,534 to Chapper discloses a universal coupling. The patent states, for example, "The invention comprises broadly the combination of a socket firmly attached to a shaft, a ball snap-fitted into the socket, a driving rod firmly attached to the ball, a second ball in which the other end of said driving rod is longitudinally movable, a second socket engageable with the second ball, and a second shaft firmly attached to the second socket."
U.S. Pat. No. 1,906,057 to Guy discloses, for example, a "universal joint of the class in which non-metallic yieldable means is employed to transmit motion from the driving to the driven member of the joint and to permit relative angular movement for disalignment of said members."
U.S. Pat. No. 1,646,427 to Skidmore discloses, for example, "A flexible coupling for interconnecting approximately aligned shafts and comprising, a pair of coupling members adapted to be secured to the shafts, each said member having a non-circular driving face; a relatively soft elastic interconnecting element adapted to be interposed between said members and having driving faces cooperating with the driving faces of said members...." Skidmore further discloses, for example, "The side wall of the recess thus provides one or more driving faces, each of which is eccentric to the axis of rotation. One specific shape of recess which will provide the desired driving face is a hexagon."
U.S. Pat. No. 1,128,430 to Fetzer discloses, for example, "A universal joint comprising a box having a rectangular opening thereon, a shank, a head on said shank positioned within said opening, said head having rounded sides."
Universal joints are generally expensive to produce because of a need for close tolerances. Further, wear on a universal joint changes the tolerances, and tends to amplify the non-uniform velocity characteristics.
It is an object of the present invention to provide an universal joint which eliminates backlash.
It is a further object of the present invention to provide a universal joint which compensates for wear.
It is a further object of the present invention to provide a universal joint whose velocity characteristics are nearly constant.
It is a further object of the present invention to provide a universal joint that is failsafe.
It is a further object of the present invention to provide a universal joint which is relatively inexpensive to manufacture.
It is a further object of the present invention to provide a universal joint through which compressive or translational vibration cannot be transmitted.